import math
from decimal import Decimal, ROUND_HALF_UP


def resolve():
    x1, y1, x2, y2 = map(float, input().split())
    a = Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP)
    print(a)


resolve()
 import math math from decimal import Decimal, ROUND_HALF_UP def resolve():
    x1, y1, x2, y2 = map(float, input().split())
    a = Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP)
    print(a) resolve x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 a = Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP) a Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP) (math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize (math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)) Decimal math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt math sqrt (x2 - x1) ** 2 + (y2 - y1) ** 2 (x2 - x1) ** 2 x2 - x1 x2 x1 2 (y2 - y1) ** 2 y2 - y1 y2 y1 2 quantize Decimal('0.0001') Decimal '0.0001' rounding=ROUND_HALF_UP rounding ROUND_HALF_UP print(a) print a resolve() resolve def resolve():
    x1, y1, x2, y2 = map(float, input().split())
    a = Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP)
    print(a) def resolve():
    x1, y1, x2, y2 = map(float, input().split())
    a = Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP)
    print(a) resolve
import math
from decimal import Decimal, ROUND_HALF_UP


def resolve():
    x1, y1, x2, y2 = map(float, input().split())
    a = Decimal(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)).quantize(Decimal('0.0001'), rounding=ROUND_HALF_UP)
    print(a)


resolve()

